In the field of mobile communication systems, it has been studied to arrange cells having relatively small coverage in a high density in order to accommodate rapidly-increasing mobile data traffic. When coverage is reduced to the order of several meters or several tens of meters, the number of users that can be present in one cell is limited. Since the distribution of mobile date traffic changes every moment, there could be a brief moment during which there is a cell where no user performing communication is present. In such a situation, it is desirable that the base station instantly stop the output of radio waves in the cell where no user performing communication is present in order to prevent interference to other cells or reduce the power consumption. Further, when a user present in the cell performs communication, the base station needs to restart the output of radio waves in the cell where the output of radio waves have been stopped.
Non-patent Literature 1 discloses a process for turning on or off the output of radio waves in a small cell according to a change in mobile data traffic in the order of several msec to several hundred msec in the 3GPP (3rd Generation Partnership Project).